Project Description: Although there is strong evidence of genetic influence on fatal suicidal behavior, little is known about exactly what it is that is inherited and the extent to which these genetic factors may be implicated in suicide among older adults. Our long-term goal is to understand key factors that predispose toward fatal suicidal behaviors in older adults, in order that more effective preventive strategies can be developed and implemented. The objective of this application, which is the next step toward that goal, is to identify factors that moderate or mediate the expression of genetic influences on fatal suicidal behavior in late life. Our central hypothesis is that fatal suicidal behavior is influenced by genetic factors that will be more prominent in late life and that are, in part, independent of genetic predispositions toward personality traits or psychiatric disorders. The rationale for the proposed study is that a delineation of specific genetic factors that influence risk of fatal suicidal behavior in late life would both provide a conceptual framework for more focused research in the future, and provide a basis on which at-risk older individuals might be identified for preventive intervention. We plan to test our central hypothesis and accomplish the overall objective of this application by pursuing the following two specific aims: 1) Identify key factors that influence expression of genetic risk. 2) Identify mediators of genetic influence on fatal suicidal behavior. We will apply univariate and multivariate structural equation twin models to data spanning three decades from the Swedish Twin Registry, linked to data from the Swedish Inpatient Register and the Swedish Death Register. At the conclusion of the proposed study, we expect to have established the magnitude of genetic influences on suicide, whether genetic factors vary as a function of age or sex, and the extent to which genetic influences reflect genetically-predisposed neuroticism, depression, alcohol abuse, cognitive dysfunction, or as-yet-undetermined factors, providing the knowledge needed to narrow the search for specific genes or environmental factors that may increase the risk of suicide in older adults. to Public Health Facilitating research on both genetic and environmental risk factors for older adult suicide is expected to lead to improvements in our ability to detect suicide risk in this age group which, in turn, will allow preventive interventions to be developed. Knowledge of risk factors is ultimately an important first step in improving the identification and treatment of individuals predisposed to suicide. [unreadable] [unreadable] [unreadable] [unreadable] [unreadable]